What supporting details does King give to support his central idea that ”one day the South will recognize its real heroes”?

When King says, "one day the South will recognize its real heroes," he is referring to the many heroes of the Civil Rights Movement. Specifically, King cites a number of people who have engaged in civil disobedience and peaceful protest during the movement. For example, King makes connections to Mother Pollard, a senior who worked on the front lines of the Montgomery Bus Boycott. He also mentions James Meredith, who was the first African American student at the University of Mississippi (Ole Miss) when he enrolled there in 1962. King also references the countless students (high school and college), ministers, and other "everyday people" who have committed to acts of peaceful protest like the Greensboro sit-ins and other lunch counter sit-ins. King believes that their bravery, both individual and widespread, shows them to be the true heroes of the South. These people are truly serving the region by diminishing racism, which King prizes far above the contributions of "typical Southern heroes" like Confederate figureheads.
https://kinginstitute.stanford.edu/king-papers/documents/letter-birmingham-jail

https://www.africa.upenn.edu/Articles_Gen/Letter_Birmingham.html

The paragraph in which "one day the South will recognize its real heroes" is found directly references the people who peacefully protest segregation and discrimination. King names James Meredith, a civil rights icon who broke the race line with his enrollment at the University of Mississippi in 1962 as its first African American student. King alludes to Mother Pollard, who was a leader of the Montgomery bus boycott in her seventies. King also alludes to the high school and college students and pastors with the commitment to execute sit-ins at segregated lunch counters. These are all extraordinary ordinary people. Their individual and collective heroism, King predicts, will turn the tide against institutionalized racism. King claims that these people will be remembered as heroes of the South, perhaps alluding to them supplanting figures from the Confederacy in the public imagination.